The longitudinal strength of the hull girder is one of the most important strength considerations in a ship, because lack of longitudinal strength may be a direct cause of the sinking of a ship. Damage such as jack knife deformation and failure of the hull girder at midship are caused by insufficient longitudinal strength. After reviewing past important break-in-two accidents of ships, this chapter introduces several issues on which the authors paid attention in the design of the longitudinal strength of hull girders, such as rational arrangement of longitudinal members, hull steel weight and cost in association with application of higher tensile steel, stress concentration, precautions against damage at the end of long attachment on hull girders, etc.